The Internet is used to provide a variety of different forms of communication between users. Two popular forms of communication are instant messaging (“IM”) and voice communication using voice over internet protocol (“VoIP”).
Instant messaging is a computer-based communication tool in which text-based messages are exchanged between users in real-time. To use an instant messaging system, user terminals of the users must be connected to a communications network, such as the internet, and an instant messaging client application must be executed on the user terminal. The client application allows a user to initiate an instant messaging conversation with a remote user, by establishing a connection over the communications network. The user can then type a message and send it to the remote user (by pressing “enter” or actuating a “send” button), and the message is displayed in the user interface of the client of the remote user in near real-time (depending on network delays). The remote user may then subsequently type a reply and send it to the other user. The exchange of messages can continue in this way, in a similar form to face-to-face verbal conversation.
Voice over internet protocol (“VoIP”) communication systems allow the user of a device, such as a personal computer, to make calls across a computer network such as the Internet. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long distance calls. To use VoIP, the user must install and execute client software on their device. The client software provides the VoIP connections as well as other functions such as registration and authentication. VoIP systems can also be enhanced through the provision of video calling.
One type of VoIP communication system uses a peer-to-peer (“P2P”) topology built on proprietary protocols. To enable access to a peer-to-peer system, the user must execute P2P client software provided by a P2P software provider on their computer, and register with the P2P system. When the user registers with the P2P system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the P2P system without the further use of a server. In particular, the users can establish their own communication routes through the P2P system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the P2P system. The exchange of the digital certificates between users provides proof of the user's identities and that they are suitably authorised and authenticated in the P2P system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a P2P system are disclosed in WO 2005/009019.